Abstract
Timber, usually used in compression or bending, has a rather high tensile strength and can be a good material for tensile structures. This paper presents structural design of a junior high school with a timber suspension roof. As it snows heavily around the site, reducing the deformation under snow load was one of the main themes of structural design. For this purpose, steel beams were placed on the roof orthogonal to the timber beams and tension rods were set between the steel beams and the foundation. The rods introduce pretension which acts as a concentrated load on the timber beams equivalent to the distributed snow load. Under snow load, the rods lose pretension corresponding to the amount of snow, meaning the total load on the timber beams remains roughly the same, therefore the deformation is suppressed small. This pretensioning system also works to reduce the influence of unbalanced snow load.